Dispensing devices of this type are used for technical, cosmetic, pharmaceutical and medical purposes, in particular in conjunction with injections for administering medication. The dispensing devices are intended to allow the operator to safely and conveniently perform the measures to be taken for the application of the container media, allowing, for instance in the case of disposable syringes, the delivery device to be used by the patient himself. As prior art, WO 2012/113008 discloses a dispensing device of the type initially referred to, in the form of a syringe head for an injection syringe. A protective cover for the injection needle forming the dispensing orifice is provided as a control body to be operated for an extraction process. By a rotary movement of the protective cover, a connecting body bearing the injection needle is axially movable in a housing part. The housing part can be coupled to an injection cylinder in such a way that the connecting body establishes a media connection with the container, here the interior of the injection cylinder. In order to convert the rotary movement of the protective cover into the axial movement of the connecting body, in the known solution a drive part, which is connected in rotation to the protective cover and is referred to in the document as a “pinion”, has circumferential, radially projecting guide knobs. The guide knobs are arranged in the housing part that is mounted on the container, in this case on the injection cylinder. Depending on the inclination of the slotted-guide tracks, the rotational movement transmitted by coupler lamellae from the protective cover to the pinion causes the longitudinal displacement of the pinion and through this displacement the opening movement of the connecting body.
The known solution is unsatisfactory in several respects. On the one hand, the design of the coupling connection between the protective cover and the pinion entails a corresponding structural complexity. On the other hand, the reliability of the function leaves a lot to be desired, as, for the typically used polymer materials with limited stiffness, the entry of the guide knob into the slotted-guide tracks and the guidance inside the slotted-guide tracks are do not prevent jamming.
In addition, the pinion has to fit tightly over the cannula during manufacture, which can easily result in damage to the needle tip and/or to the silicone layer on the needle. That damage can directly affect the user, as such damage can easily lead to painful injections.